Hydraulic drive system

Abstract

A hydraulic drive system for a three-wheeled vehicle with drive assemblies including drive units having a single drive unit with two separate directly coupled drives and a pair of transverse drive units employing respectively separate directly coupled drives. There are hydraulic feed lines for parallel operation and for series operation, a secondary hydraulic feedline between the drive units and a secondary hydraulic feed line between the drive units and a hydraulic controller controls diverter valves for parallel and series operation. The hydraulic drive includes a steering system which senses out of line travel.

What is claimed is:  
     
       1. An hydraulic drive system for a vehicle having three independent wheel drive shaft assemblies in an essentially triangular configuration, namely a transversely arranged pair of drive shaft assemblies and a single wheel drive shaft assembly longitudinally spaced from the transversely arranged pair of drive shaft assemblies, the hydraulic drive system comprising: 
       a hydraulic pump;  
       three drive units, a first being a single drive unit and a second and a third being transverse drive units, each comprising a plurality of mechanically coupled hydraulically operated drives;  
       a hydraulic input for each drive;  
       a hydraulic output for each drive;  
       the single drive unit forming part of the single wheel drive shaft assembly;  
       each of the second and third transverse drive units forming part of one of the transversely arranged drive shaft assemblies;  
       a primary hydraulic fluid line connecting the hydraulic pump to the input of each drive of the single drive unit and to one of the drives of each of the transverse drive units;  
       a secondary fluid line connecting the output of the drive of one of the single drive units separately to the unconnected input of the drive of one of the transverse drive units;  
       a further secondary fluid line connecting the output of the drive of the other single drive unit separately to the unconnected input of the drive of the other transverse drive unit;  
       a return hydraulic fluid line connecting the output of each drive of the transverse drive units to the hydraulic pump;  
       by-pass hydraulic fluid lines each connecting across each secondary hydraulic fluid line and the return hydraulic fluid lines;  
       an on/off diverter valve mounted in each by-pass hydraulic fluid line, the diverter valve in the closed position causing the drive units connected by the secondary fluid line to operate in series;  
       means for detecting movement of the vehicle out of in line travel; and  
       means for operating the on/off diverter valves over a predetermined delay to cause the drive of the single drive shaft assembly connected to the drive of the transverse drive unit to operate in parallel therewith upon the vehicle turning and to cause the other drive of the single drive shaft assembly to operate in series with the other transverse drive unit.  
     
     
       2. An hydraulic drive system as claimed in  claim 1  in which there is a time delay on the operation of the diverter valves on detecting movement of the vehicle out of in-line travel. 
     
     
       3. An hydraulic drive system as claimed in  claim 1  in which the diverter valves open gradually on detecting movement of the vehicle out of in-line travel by detecting the single drive shaft assembly out of in-line travel. 
     
     
       4. A hydraulic drive system as claimed in  claim 1  in which the diverter valves deliver hydraulic fluid through flow-restrictors. 
     
     
       5. An hydraulic drive system as claimed in  claim 1  in which the diverter valves deliver hydraulic fluid through flow restrictors having orifices mounted in a fluid line fed by the diverter valve. 
     
     
       6. An hydraulic drive system as claimed in  claim 1  in which there is a time delay of between 0.5 and 3.0 seconds between detecting of movement of the vehicle out of in-line travel and the full operation of the diverter valves. 
     
     
       7. An hydraulic drive system as claimed in  claim 6  in which the time delay is approximately 1.0 seconds. 
     
     
       8. An hydraulic drive system as claimed in  claim 1  in which the diverter valves are positive displacement piston valves. 
     
     
       9. An hydraulic drive system as claimed in  claim 1  for which a pressure release valve is provided in each secondary hydraulic feed line. 
     
     
       10. An hydraulic drive system as claimed in  claim 1  in which the steering system incorporates a steering mechanism connected to the single drive shaft assembly for steering by pivoting the single drive shaft assembly. 
     
     
       11. An hydraulic drive system as claimed in  claim 10  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly. 
     
     
       12. An hydraulic drive system as claimed in  claim 10  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly and in which the means for detecting movement of the vehicle out of in-line travel includes pivot sensing means for the steering shaft. 
     
     
       13. An hydraulic drive system as claimed in  claim 10  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly and in which the means for detecting movement of the vehicle out of in-line travel includes pivot sensing means for the steering shaft and in which the pivot sensing means comprises a pair of electrical switches each connected to a relay for operation of one of the diverter valves and a switch actuator for each switch operable on pivoting of the single wheel drive shaft assembly into a turning mode. 
     
     
       14. An hydraulic drive system as claimed in  claim 10  in which there is a time delay on the operation of the diverter valves on detecting movement of the vehicle out of in-line travel. 
     
     
       15. An hydraulic drive system as claimed in  claim 10  in which the diverter valves open gradually on detecting revolving of the single drive shaft assembly for out of in-line travel. 
     
     
       16. An hydraulic drive system as claimed in  claim 10  in which the diverter valves deliver the hydraulic fluid through flow-restrictors. 
     
     
       17. An hydraulic drive system as claimed in  claim 10  in which the diverter valves deliver the hydraulic fluid through flow restrictors having orifices mounted in a fluid line fed by the diverter valve. 
     
     
       18. An hydraulic drive system as claimed in  claim 10  in which there is a time delay of between 0.5 and 3.0 seconds between detecting of movement of the vehicle but of in-line travel and the full operation of the diverter values. 
     
     
       19. An hydraulic drive system as claimed in  claim 18  in which the time delay is approximately 1.0 seconds. 
     
     
       20. An hydraulic drive system as claimed in  claim 10  in which the diverter valves are positive displacement piston valves. 
     
     
       21. An hydraulic drive system as claimed in  claim 10  for which a pressure release valve is provided in each secondary hydraulic feed line. 
     
     
       22. An hydraulic drive system for a vehicle having three independent wheel drive shaft assemblies in an essentially triangular configuration, namely a transversely arranged pair of drive shaft assemblies and a single wheel drive shaft assembly longitudinally spaced from the transversely arranged pair of drive shaft assemblies, the hydraulic drive system comprising: 
       a hydraulic pump;  
       three drive units, a first being a single drive unit and a second and a third being transverse drive units, each comprising a plurality of mechanically coupled hydraulically operated drives;  
       a hydraulic input for each drive;  
       a hydraulic output for each drive;  
       the single drive forming part of the single wheel drive shaft assembly;  
       each of the second and third transverse drive units forming part of one transversely arranged drive shaft assemblies;  
       a primary hydraulic fluid line connecting the hydraulic pump to the input of each drive of the single drive unit and to one of the drives of each of the transverse drive units;  
       a secondary fluid line connecting the output of the drive of one of the single drive units separately to the unconnected input of the drive of one of the transverse drive units;  
       a further secondary fluid line connecting the output of the drive of the other single drive unit separately to the unconnected input of the drive of the other transverse drive unit;  
       a return hydraulic fluid line connecting the output of each drive of the transverse drive units to the hydraulic pump;  
       by-pass hydraulic fluid lines each connecting across each secondary hydraulic fluid line and the return hydraulic fluid lines;  
       an on/off diverter valve mounted in each by-pass hydraulic fluid line, the diverter valve in the closed position causing the drive units connected by the secondary fluid line to operate in series;  
       a substantially vertically arranged steering shaft mounting the single drive shaft;  
       means for pivoting the single drive shaft assembly and pivot sensing means for detecting movement of the steering shaft and hence movement of the vehicle out of in-line travel;  
       means for operating the on/off diverter valves over a predetermined delay to cause the drive of the single drive shaft assembly connected to the drive of the transverse drive unit to operate in parallel therewith upon the vehicle turning and to cause the other drive of the single drive shaft assembly to operate in series with the other transverse drive unit.  
     
     
       23. An hydraulic drive system as claimed in  claim 22  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly and in which the means for detecting movement of the vehicle out of in-line travel includes pivot sensing means for the steering shaft and in which the pivot sensing means comprises a pair of electrical switches each connected to a relay for operation of one of the diverter valves and a switch actuator for each switch operable on pivoting of the single wheel drive shaft assembly into a turning mode. 
     
     
       24. An hydraulic drive system as claimed in  claim 22  in which there is a time delay on the operation of the diverter valves on detecting movement of the vehicle out of in-line travel. 
     
     
       25. An hydraulic drive system as claimed in  claim 22  in which the diverter valves open gradually on detecting movement of the single drive shaft assembly out of in-line travel. 
     
     
       26. An hydraulic drive system as claimed in  claim 22  in which the diverter valves deliver hydraulic fluid through flow-restrictors. 
     
     
       27. An hydraulic drive system as claimed in  claim 22  in which the diverter valves deliver hydraulic fluid through flow restrictors having orifices mounted in a fluid line fed by the diverter valve. 
     
     
       28. An hydraulic drive system as claimed in  claim 22  in which there is a time delay of between 0.5 and 3.0 seconds between detecting of movement of the vehicle but of In-line travel and the full operation of the diverter values. 
     
     
       29. An hydraulic drive system as claimed in  claim 28  in which the time delay is approximately 1.0 seconds. 
     
     
       30. An hydraulic drive system as claimed in  claim 22  in which the diverter valves are positive displacement piston valves. 
     
     
       31. An hydraulic drive system as claimed in  claim 22  for which a pressure release valve is provided in each secondary hydraulic feed line. 
     
     
       32. An hydraulic drive system for a vehicle having three independent wheel drive shaft assemblies in an essentially triangular configuration, namely a transversely in-line pair of drive shaft assemblies and a single wheel drive shaft assembly longitudinally spaced from the transversely arranged pair of drive shaft assemblies, the hydraulic device system comprising: 
       a hydraulic pump;  
       three drive units, a first being a single drive unit and a second and a third being transverse drive units, units each comprising two mechanically coupled hydraulically operated drives;  
       a hydraulic input for each drive;  
       a hydraulic output for each drive;  
       the single drive unit forming part of the single wheel drive shaft assembly;  
       each of the second and third transverse drive units forming part of one of the transversely arranged drive shaft assemblies;  
       a primary hydraulic fluid line connecting the hydraulic pump to the input of each drive of the single drive unit and to one of the drives of each of the transverse drive units;  
       a secondary fluid line connecting the output of the drive of one of the single drive units separately to the unconnected input of the drive of one of the transverse drive units;  
       a further secondary fluid line connecting the remaining output of the drive of the other single drive unit separately to the unconnected input of the drive of the other transverse drive unit;  
       a return hydraulic fluid line connecting the output of each drive of the transverse drive units to the hydraulic pump;  
       by-pass hydraulic fluid lines each connecting across each secondary hydraulic fluid line and the return hydraulic fluid lines;  
       an on/off diverter valve mounted in each by-pass hydraulic fluid line, the diverter valve in the closed position causing the drive units connected by the secondary fluid line to operate in series;  
       a substantially vertically arranged steering shaft mounting the single drive shaft;  
       means for pivoting the single drive shaft assembly and pivot sensing means for detecting movement of the steering shaft and hence movement of the vehicle out of in-line travel;  
       means for operating the on/off diverter valves over a predetermined delay to cause the drive of the single drive shaft assembly connected to the drive of the transverse drive unit to operate in parallel therewith upon the vehicle turning and to cause the other drive of the single drive shaft assembly to operate in series with the other transverse drive unit.  
     
     
       33. An hydraulic drive system as claimed in  claim 32  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly and in which the means for detecting movement of the vehicle out of in-line travel includes pivot sensing means for the steering shaft and in which the pivot sensing means comprises a pair of electrical switches each connected to a relay for operation of one of the diverter valves and a switch actuator for each switch operable on pivoting of the single wheel drive shaft assembly into a turning mode. 
     
     
       34. An hydraulic drive system as claimed in  claim 32  in which there is a time delay on the operation of the diverter valves on detecting movement of the vehicle out of in-line travel. 
     
     
       35. An hydraulic drive system as claimed in  claim 32  in which the diverter valves open gradually on detecting movement of the single drive shaft assembly out of in-line travel. 
     
     
       36. An hydraulic drive system as claimed in  claim 32  in which the diverter valves deliver the hydraulic fluid through flow-restrictors. 
     
     
       37. An hydraulic drive system as claimed in  claim 32  in which the diverter valves deliver the hydraulic fluid through flow restrictors having orifices mounted in a fluid line fed by the diverter valve. 
     
     
       38. An hydraulic drive system as claimed in  claim 32  in which there is a time delay of between 0.5 and 3.0 seconds between detecting of movement of the vehicle but of in-line travel and the full operation of the diverter values. 
     
     
       39. An hydraulic drive system as claimed in  claim 38  in which the time delay is approximately 1.0 seconds. 
     
     
       40. A steering system for a vehicle having three independent wheel drive shaft assemblies in an essentially triangular configuration, namely a transversely arranged pair of drive shaft assemblies and a single wheel drive shaft assembly longitudinally spaced from the transversely arranged pair of drive shaft assemblies and having a hydraulic drive system, the steering system comprising: 
       a hydraulic pump;  
       three drive units, a first being a single drive unit and a second and a third being transverse drive units, each comprising a plurality of mechanically coupled hydraulically operated drives;  
       a hydraulic input for each drive;  
       a hydraulic output for each drive;  
       the single drive unit forming part of the single wheel drive shaft assembly;  
       each of the second and third transverse drive units namely transverse drive units forming part of one of the transversely arranged drive shaft assemblies;  
       a primary hydraulic fluid line connecting the hydraulic pump to the input of each drive of the single drive unit and to one of the drives of each of the transverse drive units;  
       a secondary fluid line connecting the output of the drive of one of the single drive units separately to the unconnected input of the drive of one of the transverse drive units;  
       a further secondary fluid line connecting the output of the drive of the other single drive unit separately to the unconnected input of the drive of the other transverse drive unit;  
       a return hydraulic fluid line connecting the output of each drive of the transverse drive units to the hydraulic pump;  
       by-pass hydraulic fluid lines each connecting across each secondary hydraulic fluid line and the return hydraulic fluid lines; and  
       an on/off diverter valve mounted in each by-pass hydraulic fluid line, the diverter valve in the closed position causing the drive units connected by the secondary fluid line to operate in series, wherein the steering system comprises;  
       means for detecting movement of the vehicle out of in-line travel; and  
       means for operating the on/off diverter valves over a predetermined delay to cause the drive of the single drive shaft assembly connected to the drive of the transverse drive unit to operate in parallel therewith upon the vehicle turning and to cause the other drive of the single drive shaft assembly to operate in series with the other transverse drive unit.  
     
     
       41. A steering system as claimed in  claim 40  in which the steering system incorporates a steering mechanism connected to the single drive shaft assembly for steering by pivoting the single drive shaft assembly. 
     
     
       42. A steering system as claimed in  claim 40  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly. 
     
     
       43. A steering system as claimed in  claim 40  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly and in which the means for detecting movement of the vehicle out of in-line travel includes pivot sensing means for the steering shaft. 
     
     
       44. A steering system as claimed in  claim 40  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly and in which the means for detecting movement of the vehicle out of in-line travel includes pivot sensing means for the steering shaft and in which the pivot sensing means comprises a pair of electrical switches each connected to a relay for operation of one of the diverter valves and a switch actuator for each switch operable on pivoting of the single wheel drive shaft assembly into a turning mode. 
     
     
       45. A steering system as claimed in  claim 40  in which there is a time delay on the operation of the diverter valves on detecting movement of the vehicle out of in-line travel. 
     
     
       46. A steering system as claimed in  claim 41  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly. 
     
     
       47. A steering system as claimed in  claim 41  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly and in which the means for detecting movement of the vehicle out of in-line travel includes pivot sensing means for the steering shaft. 
     
     
       48. A steering system as claimed in  claim 41  in which the steering mechanism includes a substantially vertically arranged steering shaft mounting the single drive shaft assembly and in which the means for detecting movement of the vehicle out of in-line travel includes pivot sensing means for the steering shaft and in which the pivot sensing means comprises a pair of electrical switches each connected to a relay for operation of one of the diverter valves and a switch actuator for each switch operable on pivoting of the single wheel drive shaft assembly into a turning mode. 
     
     
       49. A steering system as claimed in  claim 41  in which there is a time delay on the operation of the diverter valves on detecting movement of the vehicle out of in-line travel. 
     
     
       50. A steering system as claimed in  claim 41  in which the diverter valves open gradually on detecting movement of the single drive shaft assembly out of in-line travel. 
     
     
       51. A steering system as claimed in  claim 41  in which the diverter valves deliver the hydraulic fluid through flow-restrictors. 
     
     
       52. A steering system as claimed in  claim 41  in which the diverter valves deliver the hydraulic fluid through flow restrictors having orifices mounted in a fluid line fed by the diverter valve.